<script type="text/javascript">
var fd = new FormData();
fd.append( "ModelName[image]", $("#upload-form")[0].files[0]);
$.ajax({
        url: url,
        type: 'POST',
        cache: false,
        data: fd,
        dataType: "json",
        processData: false,
        contentType: false,
        success: function (data) {
        }
});
</script>

<?php
$form = $this->beginWidget(
    'CActiveForm',
    array(
        'id' => 'upload-form',
        'enableAjaxValidation' => false,
        'htmlOptions' => array('enctype' => 'multipart/form-data'),
    )
);
// ...
echo $form->labelEx($model, 'image');
echo $form->fileField($model, 'image');
echo $form->error($model, 'image');
// ...
echo CHtml::submitButton('Submit');
$this->endWidget();
    
?>